1. Field of the Invention
The present invention relates to a method and an apparatus for recording information onto an optical recording medium such as an optical disk. More specifically, the present invention relates to a method and an apparatus that are effective to set an optimal recording condition by a smaller number of times of test recording for determining a recording condition.
2. Description of the Related Art
When information is recorded on an optical recording medium such as a CD-R or a DVD-R, matching between a medium on which information is to be recorded and a recording apparatus (hereinafter referred to as a drive) used for recording depends on individual combination. This is due to factors relating to the medium, such as variation in optimal recording condition due to difference in the type of recording material of the medium or due to variation that occurs in film formation during manufacturing, and due to factors relating to the drive, such as variation in optimal recording condition due to variation that occurs in assembly during manufacturing or due to difference in the type of pickup or semiconductor laser included in the drive. Actually, a recording condition that is suitable for each combination of a medium and a drive is determined by a combination of these factors.
Thus, according to a conventional method, test recording is carried out using a combination of medium and drive that is actually used for recording, and a recording condition with which most favorable recording quality is achieved is selected.
Recording condition is mainly controlled based on the power of laser with which a medium is irradiated (hereinafter referred to as power) and the width of recording pulses (hereinafter referred to as pulse width). Thus, in order to find an accurate optimal condition, it is ideal to test all the combinations of power and pulse width. However, a test recording area provided on a medium is restricted and increase in the number of times of testing affects a size of area to be used by a user or the number of additional recording operation available. Thus, it is desired to find an optimal recording condition by a minimum number of times of testing.
Thus, conventionally, ID information that allows a drive to identify the type of medium is stored in the medium itself, and test conditions prepared in advance for individual media types are stored in the drive. When information is actually recorded, ID information of a medium loaded onto the drive is read from the medium, and a test condition associated with the ID information is used.
FIG. 31 is a schematic diagram showing features of a method for determining a test condition based on ID information stored on a medium. As shown in FIG. 31, in which a range of test condition is expressed by a matrix image of a combination of power and pulse width of recording pulse 10, the method uses test conditions in which the power is changed gradually while the pulse width is fixed.
FIG. 32 is a schematic diagram showing playback characteristics obtained by the conventional method shown in FIG. 31. As shown in FIG. 32, when power is changed by the conventional method shown in FIG. 31, playback characteristics to be obtained, such as jitter values, are represented by a characteristics curve having a pole at a certain power value, and the minimum value is selected as an optimal recording condition. This method is most generally used to determine a test condition, and improvements of this method have been proposed as described below.
FIG. 33 is a schematic diagram showing features of a method disclosed in Japanese Patent No. 3024282. As shown in FIG. 33, according to the method, a range for changing power is restricted based on a temperature of an optical disk, or based on information regarding an optimal recording condition, that are recorded in advance on an optical disk. This method is effective to reduce the number of times of testing.
According to the method, however, matching between an optical disk on which information is to be recorded and a drive used for recording is not actually examined. Since information that serves as a basis for restricting test range is estimated information such as temperature, the probability that an optimal condition exists in the restricted test range is low, so that the method is not sufficient to find an optimal condition by a small number of times of testing. Furthermore, similarly to the conventional method described earlier, an optimal condition could be missed because it is a method in which only the power is changed.
FIG. 34 is a schematic diagram showing features of methods disclosed in Japanese Unexamined Patent Application Publications No. 2000-36115, No. 2000-182244, and No. 2003-203343. These methods focus on changing pulse width, and pulse width is changed while the power is fixed.
According to these methods, however, since pulse width is changed within a wide range, the number of times of testing is not sufficiently reduced. Furthermore, since test recording is carried out with the power fixed, the methods are not sufficient to find an optimal condition.
As a method effective to reduce testing time, paragraph [0030] of Japanese Patent No. 3024282 describes “ . . . with the same configuration shown in FIG. 1, it is possible to use a wide range of test conditions for the first test recording and determine an optimal recording condition with a low precision, and then determine an optimal recording condition at a higher precision at each time of test recording until desired recording quality is obtained or an optimal recording condition of a desired precision is found. This is effective to reduce the length of time needed to find an optimal recoding condition when optimal recording condition considerably varies depending on combination of optical disk recording apparatus and optical disk, and optimal recording condition must be determined at a high precision.” This method, however, only repeats testing at different precisions. Thus, unless playback quality is checked at the first time of test recording, the number of times of testing is not sufficiently reduced even if playback quality is tested at the second time of testing.